4 ohms, 8 ohms, WTH???

[keeperthumpin]

Hi All,

New here, this is my first post so please be gentle.

I am in the process of deciding on a new head or combo. I want to go with GK for the GK tone is just what I'm after. My first amp was a p.o.s. behringer 4500 i think it was (haven't even looked at it for a long time). I paired this new with a new GK 115 cab. This cab is 400w 8 ohm.I quit using this whole setup because I came across a Hartke 3500 with a Crate 18 X 2-10 which has sounded pretty well but cant get the mellow sound I want. It is quite harsh sounding. If I run the Hartke with my GK 115, the bottom sounds great, but very minimal on the higher end.

So, since I want to stick with my 115 and add another 2-10 and head or combo 210, I am now thinking of the GK MB210 combo. The specs state that this amp puts out 500w at 4 ohms and 350w at 8 ohms. I don't understand how the 4ohm to 8 ohm thing works. I read that if this combo is not plugged into an external 8 ohm cab, you will not see the true 500w. Is this true, or will I only get 350w out of it if I do plug into my 8 ohm 115?

Any help on this ohm stuff would be greatly appreciated.

[christw]

It has an external jack that allows you to add another 8 ohm speaker cabinet in parallel, lowering the total resistance to 4 ohms.

If you're interested, the formula for adding parallel resistances is: 1/R1 + 1/R2 = 1/Rtotal

R1 = 8 ohms (it's own 2x10's)
R2 = 8 ohms (your 115)
1/8 + 1/8 = 1/Rt so Rt = 4 ohms.

The formula also applies with more parallel resistances.

It will produce 350 watts into it's self contained 8 ohm load (the two ten's). If you add an 8 ohm extension cabinet and lower the total resistance to 4 ohms it will produce it's full 500 watts with 250 to it's internal speakers and 250 to the external cabinet.

I'm trying to find a good FAQ set on impedance through google for you but not succeeding...

[GRAHAM SG1]

I have got an MB210 and am waiting for my new MBE115 to be delivered, will let you know what it sound slike, looking forward to getting the full 500 Watts and the extra sound from the 15"
I wanted an MBE210 but they are very hard to get in the UK .

[keeperthumpin]

christw,

Thank you for the great explanation. It all makes sense now.

Graham SG1,

How do you like the MB210 on its own? Also, as a member of the Gibson club and SG1 as part of your name, I take it you have an SG. How do you like it too? I want a Gibson SG soooo baaad!! I have a G&L SB-2 now and love it but the faded SG will be next.

[mcapote]

I got the MB210 and It works just fine, I was actually surprised that I was able to use it by itself and keep up with my guitarist and PAed drummer no problem.

[keeperthumpin]

Awesome. The crew I'm in is quite loud!! Good to know its pretty good on its own.

[dvh]

Originally Posted by christw

I'm trying to find a good FAQ set on impedance through google for you but not succeeding...

What about the sticky on this very site?
AMPS FAQ!! Info on OHMS, Allsize RIGS-OverUnderPowerCabs DIY TechTalk-Links